1. Field of the Invention
The present invention relates to a photosensitive resinous material suitable particularly for fluorescent screens of cathode ray tubes such as color or black-and-white television picture tubes.
2. Brief Description of the Prior Art
Fluorescent screens of color television picture tubes are usually coated with a light-absorbing material such as carbon between their fluorescent layers to ensure a favorable contrast of color pattern by preventing the light from scattering or reflecting. To form a pattern of light-absorbing material, conventional technique involves coating a polyvinylalcohol containing a dichromate on the inner surface of the face plate of a cathode ray tube, converting portions of the polyvinylalcohol layer into the water-insoluble material by means of selective exposure to light, removing the unexposed portions by washing them with water, coating the light-absorbing material containing graphite and then removing both the polyvinylalcohol layers and the light-absorbing layers superposed thereon by the aid of a H.sub.2 O.sub.2 aqueous solution followed by the washing with water. This technique can allow the light-absorbing material layers to be left coated directly on the portions of the face plate corresponding to the unexposed or uncured portions which were previously removed. The portions of the inner face plate surface between the light-absorbing layers are then coated in turn with fluorescent slurries comprising polyvinylalcohol, a photosensitive resin containing a dichromate, and an illuminating fluorescent substance in red, green or blue color, respectively. The coating is then exposed to light, developed and subsequently baked to form a desired fluorescent pattern in the given color. This technique is repeated to form a fluorescent screen having fluorescent red, green and blue colors.
In conventional technique of forming patterns of a light-absorbing and/or fluorescent material, a dichromate has been employed as a photosensitive agent so that a velocity of curing by exposure to light is not sufficiently fast and accordingly a longer period of light exposure or an amount of light and/or a source of light having a stronger energy is required. These are practically inadvantageous economically or in productivity. The use of the dichromate also presents drawbacks that it rather adversely interferes with an illumination efficiency of fluorescent materials to be employed and that it may cause a pollution resulting from chromium. There is also a room for improvement in an adherence strength of the polyvinylalcohol layer to the face plate of a cathode ray tube.